The invention relates to an apparatus for the treatment of liquids, such as for coalescing liquid droplets that are dispersed in an emulsion. The invention relates in particular to a fibrous bed coalescer which is a permeable bed of fibers.
Fibrous bed coalescers are commonly used in the oil and gas industry for coalescing oil droplets which are dispersed in an oil-in-water emulsion. Reference may be had to U.S. Pat. No. 3,810,832, West German Pat. No. 2,923,779, Soviet Union Pat. Nos. 567,463 and 816,497, and British Pat. No. 2,018,610. The coalescer of the British patent comprises a layer of fibers held under pressure between a pair of perforated plates. The plates are arranged at an adjustable mutual distance and in a lateral sense with respect to the flow path of the fluid to be treated, thereby creating a fibrous bed with an adjustable density and permeability. Although the performance of the known fibrous bed coalescer is satisfactory, it appeared that there were a number of potential high-shear zones where re-dispersion of coalesced droplets could occur. One such zone occurs in the area of the downstream plate where the coalesced droplets travel through the perforations in the plates at high speed. Another problem envisaged with the known apparatus is that the layer of fibers must frequently be cleaned because during operation solid contaminants present in the liquid may agglomerate in the narrow fluid channels between the fibers, thereby clogging the fibrous bed and reducing the coalescence efficiency.